The present invention relates to expansion valves for controlling flow of refrigerant between the exothermic heat exchanger or condenser and the endothermic heat exchanger or evaporator in a refrigeration or air conditioning system. Valves of this type are employed for creating a sufficient pressure drop and expansion of the refrigerant prior to entry into the evaporator.
Refrigeration systems of this type typically consist of a compressor to compress the refrigerant vapors, a condenser to condense compressed refrigerant vapors to liquid, an expansion valve, and an evaporator in which low pressure refrigerant liquid is vaporized, in connection with which the medium surrounding the evaporator coils is cooled.
Various types of expansion valves are known in the prior art, including both mechanically-actuated and electrically-actuated valves. These types are described in U.S. Patent and Trademark Office Ser. No. 188,017, filed Apr. 29, 1988, the disclosures of which are hereby incorporated by reference.
Electrically-actuated expansion valves typically operate by pulsing refrigerant material through the valve at a pulse rate controlled by the frequency with which a certain member of the valve oscillates back and forth. One problem common to electrically-actuated refrigerant expansion valves is the creation of excessive noise at the expansion valve for a short period of time after the compressor is energized. This problem appears to be caused by the presence of vaporous refrigerant rather than liquid refrigerant at the inlet port of the expansion valve at the time of start up. These vapors cause audible flow noise when pulsed through the expansion valve at the normal working frequency of the expansion valve. This audible noise persists until the vaporous refrigerant is pulsed through the expansion valve and only liquid refrigerant is present at the inlet expansion valve orifice. The audible noise is also reduced as the compressor, after being energized, begins to build pressure in its outflow line, which increase in pressure causes vaporous refrigerant in the condenser to liquify and also pushes liquid refrigerant closer to the expansion valve inlet orifice.
Prior art does not deal with this excessive noise problem; the problem has simply been tolerated without resolution.